1. Technical Field of the Invention
The invention relates to a method for drying a thick wet layer coated on one face of a cardboard sheet, the method being of the type in which the coated cardboard sheet is fed continuously and a high frequency electric field is applied thereto in such manner that the lines of force of said electric field go only through said thick layer to selectively heat said layer.
2. Discussion of the Prior Art
There is disclosed in German Pat. No. 730,782 an apparatus for selectively drying by high frequency heating the surface portion of a plate. This apparatus comprises two electrodes of opposite polarities disposed along the longitudinal side edges of the plate. With such an arrangement, the lines of force of the high frequency electric field concentrate in the surface portion and a selective drying is achieved.
The drying thus obtained is so active and rapid, however, that ionized particles tend to be attracted out of the layer by field effect so that they are deposited on the electrodes and stain the same.